Conventionally, there have been known apparatuses that recover heat energy generated by internal combustion engines for ships. As an example of such apparatuses, an exhaust-heat recovery-type ship propulsion apparatus disclosed in Japanese Unexamined Patent Publication No. 2013-180625 has an exhaust-heat recovery power-generation system with a first cycle that causes an organic fluid to circulate through a high-pressure evaporator, a power turbine for power generation, and a condenser in this order by means of a first circulation pump and a second cycle that causes the organic fluid to circulate through a low-pressure evaporator, the power turbine, and the condenser in this order by means of a second circulation pump. The low-pressure evaporator heats the organic fluid from the second circulation pump with jacket cooling water used to cool the jacket of a diesel engine, and the high-pressure evaporator heats the organic fluid from the first circulation pump by heat exchange between steam supplied from an exhaust-gas economizer and exhaust gas from the diesel engine. In the exhaust-heat recovery power-generation system, a generator connected to the power turbine generates power when the power turbine is driven to rotate based on the heat drop of the organic fluid evaporated by the low-pressure evaporator and the heat drop of the organic fluid evaporated by the high-pressure evaporator.
Meanwhile, the steam generated by the exhaust-gas economizer is preferentially supplied to a destination that demands the steam, other than the exhaust-heat recovery power-generation system, in a ship, e.g., a soot blower or the like that cleans a ballast tank, a cargo room, a deck, or the like. Thus, a supply amount of the steam from the exhaust-gas economizer to the evaporator of the exhaust-heat recovery power-generation system, i.e., a heat energy recovery system decreases, which results in a likelihood that the organic fluid is supplied to the power turbine without being substantially heated. Therefore, in such a case, an operator performs a stop operation to stop the operation of the heat energy recovery system.
However, it is difficult for the operator to perform the stop operation of the heat energy recovery system at an appropriate timing, and there is also a possibility of the operator forgetting to stop the operation of the heat energy recovery system.